The intrapulmonic air pressure exceeds the extrapulmonic intrapleural pressure under normal physiologic conditions, thus constituting the negative intrathoracic pressure deemed necessary for proper lung expansion. But when pleural air accumulates outside the lung, the negative pressure dynamics are disrupted, and the lung will begin to deflate unless emergency evacuation of pleural air is accomplished. Pneumothorax is usually spontaneous, but may follow trauma such as barotrauma from mechanical ventilation as applied to distressed neonates. Normally the outer epithelial lining of the lung, the visceral pleura, adheres to the inner epithelial lining of the chest wall, the parietal pleura, separated by only a potential space normally uninvaded by air as long as physiologic negative pressure dynamics keep the lungs inflated. Tension pneumothorax results from bronchopulmonary injury which acts as a one way valve permitting the abnormal egress of air into the pleural space, causing extrapulmonic air trapping which is aggravated by positive pressure ventilation or bagging. In distressed artificially ventilated neonates who suddenly worsen, life support trainees are mindful of the acronym DOPE which represents Displacement of the endotracheal tube, Obstruction, Pneumothorax, and Equipment failure. A quick inventory of breath sounds and mechanical equipment can rule out displacement, obstruction, and equipment failure, but pneumothorax must be suspected when an infant suddenly deteriorates after initially responding to positive pressure ventilation, manifests unilateral decrease in chest wall expansion, altered intensity or pitch of breath sounds, and increased resistance to manual ventilation. One may find mediastinal shift, decreased breath sounds on the involved side, homolaterally distended neck veins, contralateral tracheal deviation. Pneumothorax and especially tension pneumothorax are life threatening emergencies which demand prompt intervention. Prior to chest tube or catheter placement, noninvasive treatment includes oxygen and parenteral volume expanders, and one should check the blood glucose and oxygen saturation.
If time permits, one can order a chest film with crosstable lateral view. Radiographically one may see a thin sharp white line representing pleura, absent parenchymovascular markings beyond the pleura, air beyond the pleura represented by a dark lucency, increased lucency over one lung field, a deep sulcus sign at the lateral costophrenic angle in the case of a basilar pneumothorax, increased sharpness of the mediastinal border in the case of a medial pneumothorax, anterior lucency on the crosstable lateral with pneumomediastinum, or depressed hemidiaphragm on the homolateral side with tension pneumothorax. If one suspects pneumothorax and there is insufficient time to obtain an Xray, chest transillumination may be attempted for confirmation. With or without an Xray, if clinical suspicion persists, one locates the 2nd intercostal space in the midclavicular line, or the 5th intercostal space in the anterior axillary line, bearing in mind that the nipple is at the 4th intercostal space. Currently utilized procedures typically include prepping the skin with povidone or chlorhexidine, infiltrating intradermal lidocaine, inserting a catheter-covered needle through the chest wall, withdrawing the needle, and connecting the indwelling intrapleural catheter to a one-way valve or waterseal.
Pneumothorax occurs in 2% of all neonates, or about 40,000 of the nearly two million births annually in the US, 19% of all neonates with respiratory distress syndrome (RDS), at least 20% of RDS neonates treated with continuous positive airway pressure, and 36% of neonates with meconium aspiration. In addition to RDS and meconium aspiration, risk factors for neonatal pneumothorax include transient tachypnea of the newborn, perinatal asphyxia, cardiopulmonary resuscitation with mechanical ventilation, and elective cesarian section. Among normal term infants delivered electively by cesarian section, pneumothorax occurs at a rate of 2.9/1000 in such babies (J Ped 2007; 150:252). Elective cesarian section is an obstetrical modality which is gaining in popularity in both the US and UK. Cesarian deliveries overall approach a half million per year in the US, most of them elective. Aspirated meconium may act as a one-way valve and result in tension pneumothorax.
Pneumothorax is a frequent concomitant of these conditions and must be recognized and treated promptly. Neonatal pneumothorax likewise requires immediate recognition and treatment, hopefully minimizing instrumentation and trauma. Nonsurgical management includes endotracheal visualization and suction of meconium as needed, oxygen, circulatory volume expansion, management of associated infection and hypoglycemia, Narcan if indicated, and other appropriate supportive measures.
Pneumothorax in all age groups is a medical emergency, and particularly so in the neonate in whom clinical deterioration typically occurs at an alarming rate. Tension pneumothorax rapidly worsens with mechanical ventilation, as its one-way valve and malignant air trapping quickly result in mediastinal shift and diminished venous return which impair diastolic filling. Ultimately the plummeting cardiorespiratory function will be fatal without prompt intervention, and the urgency inherent in pneumothorax management requires that any treatment device not entail any undue expenditure of time summoning extra personnel and equipment.
There is an ongoing need for a compact rescue device that can be quickly and safely implemented by relatively inexperienced personnel for the immediate treatment of pneumothorax, particularly neonatal pneumothorax and tension pneumothorax, in situations involving respiratory distress, meconium aspiration, perinatal asphyxia, transient tachypnea of the newborn, or any scenario which includes artificial ventilation and bagging in the delivery room or neonatal intensive care unit.